Role of the metal sites of a heterobimetallic trinuclear complex on DNA binding and cleavage activities

Abstract

Reaction of (PPh₄)[Fe(pzcq)(CN)₃] with cobalt(II) nitrate afforded a heterobimetallic trinuclear complex [Fe(pzcq)(CN)₃]₂[Co(H₂O)₂(MeOH)₂]∙2H₂O (1), where Hpzcq is 8-(pyrazine-2-carboxamido)quinoline. The structural data show that crystallographically equivalent [(pzcq)Fe(CN)₃]⁻ units are monodentate ligands through one of the three cyanides to cobalt(II) in 1. Interaction of 1 with calf thymus DNA was investigated through UV–vis and fluorescence spectroscopic methods and viscosity measurements. Complex 1 preferably binds with CT-DNA in the groove region and promotes DNA cleavage in the presence of H₂O₂ as an activating agent. The DNA cleavage proceeds through an oxidative pathway possibly through a diffusible hydroxyl radical mechanism. The nuclease activity of 1 can be explained by cooperation of two different metal sites, the aromatic rings of pzcq in iron(III) are responsible for binding with DNA, while diffusible hydroxyl radical generated in situ by the reaction of cobalt(II) center with hydrogen peroxide is likely to be involved for cleavage of DNA.

Keywords:

• Heterobimetallic trinuclear complex
• DNA binding
• Nuclease activity
• Role of metal sites

Acknowledgements

The author is thankful to the University Grant Commission (UGC), India (Sanction No. PSW-173/11-12) for financial support for this work. Instrumental facilities from Jadavpur University, India are also gratefully acknowledged.